Replacing the wheel bearings: Difference between revisions

[[Category:Final Drive]]

Wheel bearings are generally treated in an “out of sight, out of mind” manner, but these few little pieces of metal are what keep your wheels going round and round.

When inspecting, keep these things in mind. If they're notchy (don't turn smoothly) when you turn the wheel by hand, they need to be replaced. Also, if there's any lateral play (the wheel moves side-to-side) they need to be replaced. They should be a little stiff to turn by hand, but not very stiff if you're rolling the wheel while it's still on the bike. Bearings are dirt cheap to replace, and should be done if there is any question.

What you'll find when you pull the wheel off and look are two bearings and a tube of some soft metal that runs between the inner races. When you snug the axle down, it pulls everything tight on the center race of the wheel bearing, and that should be the ONLY place it's tight. But stock bearings are only sealed on one side and usually won't last the life of the bike. You want to replace them with double sealed bearings. These will have the same part number, but will have an SS or ZZ at the end of the number.  

For more information on bearings, see [[A brief guide to bearings|this FAQ article]].

Wheel bearings are simple. You'll want two small sections of 2x4, or a milk crate (same stuff you'd use for [[Mounting & balancing tires yourself|changing tires]]) to hold the rotor off the ground. For removal, the Motion Pro [http://www.motionpro.com/motorcycle/tools/bearing_remover_sets 8 Piece Metric Bearing Remover Set], or something similar, is the correct tool for the job. The short piece fits in the axle opening. The long piece has a wedge that fits in the slot of the short piece, which allows the whole thing to 'grab' the inner race. Then, as you beat on it with a hammer, it should work the whole bearing out evenly (it doesn't always, but it works better than anything else.) As usual with Motion Pro, Googling should yield a better price than the MP site.  

If you don't want to spend the money on the tool set, you can sometimes get by with a drift (aka a punch), or a long 3/8 drive extension. Some have had success with a BFSD (large screwdriver). Some have had no success and ended up getting the Motion Pro tool. Since you're not trying to save the old ones, feel free to bash away at the inner race. The tube that runs through the wheel doesn't usually completely cover the inner race, so you can kind of get a purchase on it, beating the bearing out from the opposite side of the wheel. The down side is that you have to move around the race to get the bearing out evenly, and you're going to have to be careful, because the drift will probably slip off and bust your knuckles a few times (think "leather gloves").

One tool that makes installation/removal easier is a forced air shop heater. Hold the wheel hub in front of it until it's around 200 deg F. The expansion from the heat makes it marginally easier to remove the old bearings. This also works for installation. Leave the new bearings in your freezer until you're ready for installation, and install them into the heated hub. It reduces the amount of interference just enough to make it easy to tap in the new bearings.

You can use a heat gun on the hub to expand it. Otherwise, a bit of metal may be removed every time you remove or replace a bearing. Some wheels even get ruined this way.

The heat gun works like this: The wheel (and the hub, where the bearing goes) is made of aluminum, while the bearing is made of steel. Aluminum expands faster than steel, so even if both are heated to the same temperature, the interference fit relaxes and the bearing becomes easy to remove. Again, leave the new bearings in your freezer until you're ready for installation, and install them into the heated hub.

For putting the new bearings in, all you need to do is hammer them in. '''Important:''' ''You only want to put pressure on the outer race (the outside rim of the bearing)''. You can do this with a bearing seating kit (check auto parts stores), or a socket that you carefully hold in place so you don't hit the bearings. You can also disassemble an old bearing and use only the outer race, with a piece of wood on top of it, to drive the new bearing in.